Considering how long our system's giants' orbital periods are (jupiter is 12 years, the rest are even longer), then kepler wasn't even up there long enough to see ONE transit of a giant at the distance they are in our system, let alone 3 of them.

Considering how long our system's giants' orbital periods are (jupiter is 12 years, the rest are even longer), then kepler wasn't even up there long enough to see ONE transit of a giant at the distance they are in our system, let alone 3 of them.

RIP Kesler - may you enjoy your afterlife adventures with Spirit.

It's quite possible we saw singular transits of planets with large orbital periods. It just depends on where they were in their orbit when Kepler started looking (kinda like it would have been a long time until we discovered Neptune if it and Uranus hadn't been the respective parts of their orbits where they affect each other). But you need a second transit to have any clue that it wasn't a one-off event, maybe from something occluding the star that isn't even in that star system, and 3 to know that it's periodic and not two unrelated occlusions.

To identify a candidate, Kepler needs to see it pass between Earth and the star the exoplanet orbits three times.

Isn't it possible that there could be loads of planets, that will never pass between Earth and the star? Or is there something that ensures all planetary orbits are aligned along the same 2d plane? We live in a 3D universe, so I'd expect it to be likely that a great deal of orbits could be more vertical than horizontal.

Considering how long our system's giants' orbital periods are (jupiter is 12 years, the rest are even longer), then kepler wasn't even up there long enough to see ONE transit of a giant at the distance they are in our system, let alone 3 of them.

One of the notable things about the Kepler data is that a number of planets that orbit very close to their host star. There are a few systems that have multiple planets packed in close to the host - closer than where Mercury is to the Sun.

To identify a candidate, Kepler needs to see it pass between Earth and the star the exoplanet orbits three times.

Isn't it possible that there could be loads of planets, that will never pass between Earth and the star? Or is there something that ensures all planetary orbits are aligned along the same 2d plane? We live in a 3D universe, so I'd expect it to be likely that a great deal of orbits could be more vertical than horizontal.

There is nothing that ensures it. If you are more than about 1.5-2.2 degrees out of the plain Kepler will not see it. Then again, Kepler was monitoring a star field of roughly 150k stars, so we still got a few thousand planetary candidates.

Is it just me or was this an unusually short service life? 2009-2012 isn't nearly long enough, we'd have had to get lucky to catch 3 transits of a 1 AU orbit around a sun-like star.

Kepler's Prime Mission was 3.5 years, which gives a 50% chance of catching 3 transits of a planet with a 1-year orbit. It did exceed this time.

One problem though was that shortly after Kepler began studying the stars we learned something from it -- most stars have more sunspot activity than our sun, and so their brightness naturally varies more than our assumptions. Which means more noise. Which means 4 transits were needed to be sure of what we were seeing. So that means we'd have needed a longer mission to have achieved Kepler's original goals.

Just out of curiosity: would a smaller planet (assuming sufficient gravity to retain an atmosphere of some sort) be habitable even at the closer proximity (I assume if water is liquid its in a pretty narrow temperature range), or would other factors be problematic (like increased radiation exposure, solar flare effects, etc.)?

Just out of curiosity: would a smaller planet (assuming sufficient gravity to retain an atmosphere of some sort) be habitable even at the closer proximity (I assume if water is liquid its in a pretty narrow temperature range), or would other factors be problematic (like increased radiation exposure, solar flare effects, etc.)?

That largely depends on the host star - but yes.

Our sun is actually on the larger side compared to average, most stars are dimmer and cooler, assuring that you could live much closer to it (assuming proper atmosphere and radiation levels) than is possible in the Sol system.

Considering how long our system's giants' orbital periods are (jupiter is 12 years, the rest are even longer), then kepler wasn't even up there long enough to see ONE transit of a giant at the distance they are in our system, let alone 3 of them.

RIP Kesler - may you enjoy your afterlife adventures with Spirit.

It's quite possible we saw singular transits of planets with large orbital periods. It just depends on where they were in their orbit when Kepler started looking (kinda like it would have been a long time until we discovered Neptune if it and Uranus hadn't been the respective parts of their orbits where they affect each other). But you need a second transit to have any clue that it wasn't a one-off event, maybe from something occluding the star that isn't even in that star system, and 3 to know that it's periodic and not two unrelated occlusions.

well yeah, of course it depends on where a planet is in its rotational period. if a planet had a period of 1.5 years, then kepler might have had a chance to see two transits, depending on when it started observing that system. but for a planet with a period of even only 3 years, there's a chance that kepler might not have seen even a single transit, depending on when it first looked at that system.

i'm not trying to tear down the work done by the kepler team. for the first of its kind, it gave us lots of awesome data. and made us rethink lots of things.

There is nothing that ensures [the planet's orbit crosses between us and the star]. If you are more than about 1.5-2.2 degrees out of the plain Kepler will not see it. Then again, Kepler was monitoring a star field of roughly 150k stars, so we still got a few thousand planetary candidates.

Note that the closer the planet, and the bigger the planet, the more slack there is in that number.

I'd just like to point out that it's a pretty impressive feat to hurl a piece of complex machinery into the next best thing to absolute vacuum by way of strapping enough explosives under it's ass to blow up a middling city, then subjecting it to massive thermal differentials and radiation that your eyeballs would boil, then have it survive 4 years while pointing with a precision that makes brain surgery look crude.

i'm not trying to tear down the work done by the kesler team. for the first of its kind, it gave us lots of awesome data. and made us rethink lots of things.

Of course, your respectful RIP made that clear, and I'm not smacking you down, I'm just clarifying a pedantic point that we could have seen one transit (but wouldn't know that was what we saw). The gist of your post was completely correct, that Kepler would have had to run a *very* long time to have made a discovery of a long-orbit planet. As it is, it didn't run long enough to even discover the kind of planet we launched it with the intent of discovering (thanks to the unknown-at-launch sunspot issue).

We always hope missions run longer than we expect, and that any bad assumptions we made will be resolved in our favor, but sometimes...

Well, we just need more missions like Kepler (which I think are being planned; just can't recall any names I've heard).

I'd just like to point out that it's a pretty impressive feat to hurl a piece of complex machinery into the next best thing to absolute vacuum by way of strapping enough explosives under it's ass to blow up a middling city, then subjecting it to massive thermal differentials and radiation that your eyeballs would boil, then have it survive 4 years while pointing with a precision that makes brain surgery look crude.

(Yes, yes, I know it's not all correct. Roll with the metaphor.)

And then detect little tiny rocks from trillions upon trillions of miles away as they pass in front of massive balls of fire, by the massive balls of fire getting ever so slightly dimmer as the speck passes in front.

A lot of the effort in the EU is currently going into radial velocity surveys like HARPS now that KEPLER is closing up shop. Until we get another photometer up there, radial velocity stuff is where it will be for the most part.

I'd just like to point out that it's a pretty impressive feat to hurl a piece of complex machinery into the next best thing to absolute vacuum by way of strapping enough explosives under it's ass to blow up a middling city, then subjecting it to massive thermal differentials and radiation that your eyeballs would boil, then have it survive 4 years while pointing with a precision that makes brain surgery look crude.

(Yes, yes, I know it's not all correct. Roll with the metaphor.)

And then detect little tiny rocks from trillions upon trillions of miles away as they pass in front of massive balls of fire, by the massive balls of fire getting ever so slightly dimmer as the speck passes in front.

There is a cute fact on Kepler's web site that basically says it's like detecting (the photometric drop) a flee moving in front of a headlight that is a few miles away from you.

Just out of curiosity: would a smaller planet (assuming sufficient gravity to retain an atmosphere of some sort) be habitable even at the closer proximity (I assume if water is liquid its in a pretty narrow temperature range), or would other factors be problematic (like increased radiation exposure, solar flare effects, etc.)?

I don't think anyone really knows. But you are right that the basic definition of habitable zone does not cover the whole picture, it means only that the expected temperatures at that distance would support the existence of liquid water.

OK so since kepler isn't orbiting earth, did they equip it with de-orbiting fuel/boosters for the end of its mission? since the lagrange points are so few, we don't want to clutter them with space junk. probably wouldn't be hard to just boost it off in some random direction and let it (eventually, maybe decades/centuries from now) crash into the sun. it just needs enough to break the stability of its current orbit, right?

There is a cute fact on Kepler's web site that basically says it's like detecting (the photometric drop) a flee moving in front of a headlight that is a few miles away from you.

that's probably derived from some article or textbook i remember reading in the 80s. it said something along the lines of "trying to detect the light from a planet in another system is about as difficult as looking at a car's headlights from 5 miles away, then trying to make out the glow of the driver's cigarette... with the naked eye."

'They have a year of data from the telescope left to analyze, which should yield some exciting finds, quite possibly including an Earth-sized planet orbiting a sunlike star at a distance suitable for life. “We can’t feel sad because we have a beautiful dataset that we’re going to work on for years,” Latham says.

Combine those data with upcoming missions, plus 16 bottles of wine uncorked after the meeting presentations, and Latham says astronomers at the post-Kepler conference were upbeat about the future.

OK so since kepler isn't orbiting earth, did they equip it with de-orbiting fuel/boosters for the end of its mission? since the lagrange points are so few, we don't want to clutter them with space junk.

Kepler is not at the L5 Lagrange point. It is in a heliocentric orbit with a slightly larger orbital period than earth, so it's slowly getting farther away from us. No reason to move it.

Just out of curiosity: would a smaller planet (assuming sufficient gravity to retain an atmosphere of some sort) be habitable even at the closer proximity (I assume if water is liquid its in a pretty narrow temperature range), or would other factors be problematic (like increased radiation exposure, solar flare effects, etc.)?

As I understand it, the main problem for habitability in that scenario is that the planet would almost certainly be tidally-locked to its host star (that is, the same side of the planet would always face the host star, giving it permanent light & dark sides, same as our moon). So only a small portion of the planet would receive direct light & heat, making it very hot on the light side & very cold on the dark side.

Though there is a theory (hypothesis?) called "eyeball Earths". The idea is that heating the light side would create convection patterns that would bring heat to the dark side and at least make the twilight areas of the planet habitable.

Of course, it depends on the planet, the host star, and the relative distances between them. If a planet is so close to the host star that it's surface remains molten, then that pretty much rules out habitability.

Kepler's not dead. But unfortunately it's now a retired planet hunter. Space arrow to the knee.

so what you're saying is...

"I've experiments to run. There is research to be done. On the people who are still alive. And, believe me, I'm still alive! I'm doing science and I'm still alive! I feel FANTASTIC and I'm still alive! While you're dying, I'll be still alive! And when you're dead, I will be still alive! Still Alive! Still Alive... "

seriously though... can the kepler equipment still be used for anything, or is it too far gone now, and just idly waiting for its batteries to die?

I think Kepler was designed to validate that there were significant numbers of planets out there. Expecting to have a space telescope remain functional for 12+ years unattended is a very ambitious program. (Hubble was another thing entirely.) The expected mission length would limit the number of detectable planets to those that transited the star multiple times. I suspect the designers of Kepler were aware that there would be a range of planet orbits that wouldn't be observable.

Also there seems to be a large number of dimmer stars that have come out of the data. That might have been deliberate so that the "Goldilocks Zones" would be closer to the star and the planets in those orbits would also have more transits in the time they expected Kepler to remain functional. That factor might have been why Kepler was pointed at that particular part of the sky.

If you think of Kepler as a "field scout" for Webb, Kepler comes off looking extremely successful. Assuming Webb eventually gets to its heliospherical orbit, it will be an amazing planet spotter since it will be operating in the infrared part of the spectrum.

Regardless, I hope we send a replacement up soon. It would be really awesome to have a space telescope that can last decades. If we ever get to that point we'll be able to learn a lot more about other planets out there.